论文标题
在Z〜1.1726处出现新的HI 21-CM吸收成分朝伽玛射线Blazar PKS 〜2355-106
Emergence of a new HI 21-cm absorption component at z~1.1726 towards the gamma-ray blazar PKS~2355-106
论文作者
论文摘要
我们报告了Z_ABS = 1.172635在受阻的Lyman-Alpha吸收器（DLA）中的新HI 21-CM吸收的出现，朝向伽马射线Blazar PKS 2355-106（Z_EM 〜1.639），使用科学验证（2020年6月）从MEERKAT吸收率（2020年6月）。自2006年以来，已知该DLA在Z_ABS处显示出狭窄的HI 21-CM吸收= 1.173019与不同的金属吸收系成分相吻合。我们没有从该已知的HI组件中检测到显着的HI 21-CM光学深度变化。高分辨率光谱（2010年8月）在新的HI 21-CM吸收剂的红移处显示出独特的Mg I吸收。但是，在单一离子物种的概况中，该成分并不明显。我们测量金属性（[Zn/H] = - （0.77 \ pM0.11）和[Si/H] = - （0.96 \ pm0.11））和耗尽（[Fe/Zn] = - （0.63 \ pm0.16））。使用Si II，Fe II和MG I的表观柱密度曲线，我们表明耗竭和N（mg i）/N（SI II）柱密度比系统地在整个速度范围内有所不同。耗尽较高的区域的N（mg i）/N（Si II）比率略大。两个HI 21-CM吸收器属于此速度范围。如果在〜0.35 pc的长度尺度上存在较大的光学深度梯度，则可以理解z_abs = 1.172635的出现。但是，产生Z_ABS的气体= 1.173019组件在同一尺度上必须几乎均匀。在测量基本常数和宇宙加速度的变化的实验中，即使无线电发射显然像PKS 2355-106一样，也必须考虑测量基本常数和宇宙加速的变化的实验中，必须考虑到吸收线变异性引入的系统不确定性。
We report the emergence of a new HI 21-cm absorption at z_abs = 1.172635 in the damped Lyman-alpha absorber (DLA) towards the gamma-ray blazar PKS 2355-106 (z_em~1.639) using science verification observations (June 2020) from the MeerKAT Absorption Line Survey (MALS). Since 2006, this DLA is known to show a narrow HI 21-cm absorption at z_abs = 1.173019 coinciding with a distinct metal absorption line component. We do not detect significant HI 21-cm optical depth variations from this known HI component. A high resolution optical spectrum (August 2010) shows a distinct Mg I absorption at the redshift of the new HI 21-cm absorber. However, this component is not evident in the profiles of singly ionized species. We measure the metallicity ([Zn/H] = -(0.77\pm0.11) and [Si/H]= -(0.96\pm0.11)) and depletion ([Fe/Zn] = -(0.63\pm0.16)) for the full system. Using the apparent column density profiles of Si II, Fe II and Mg I we show that the depletion and the N(Mg I)/N(Si II) column density ratio systematically vary across the velocity range. The region with high depletion tends to have slightly larger N(Mg I)/N(Si II) ratio. The two HI 21-cm absorbers belong to this velocity range. The emergence of z_abs = 1.172635 can be understood if there is a large optical depth gradient over a length scale of ~0.35 pc. However, the gas producing the z_abs = 1.173019 component must be nearly uniform over the same scale. Systematic uncertainties introduced by the absorption line variability has to be accounted for in experiments measuring the variations of fundamental constants and cosmic acceleration even when the radio emission is apparently compact as in PKS 2355-106.
